Selectively demetalizing condenser paper



May 20, 1952 G. MELLEN ET AL SELECTIVELY DEMETALIZING CONDENSER PAPERFiled Oct. 1, 1949 INVENTORS G/enr; l. Me//e/7 Vince) C Ha J1:

ATTORNEY Patented May 20, 1952 U NI TE D ATE'S PAT EN T OF F] GESELECTIVELY DEMETALIZIN G CONDENSER PAPER Glenn L. Mellen, FraminghamCenter, and Vincent 0. Hall. J r., West Roxbury, Mass, assignors toNational Research Corporation, Cambridge,

1 Mass., a corporation of Massachusetts Application October 1, 1949,Serial No." 119,164

roiaims. (o1. 219 '19) This invention relates'to the formation of .ametal-free stripe on a web of metal-coatednonconducting sheet material,and. is particularly useful in the manufacture of electrical condensers.

In the fabrication of electrical condensers from strips of metal-coated,nonconducting sheet material, such as paper having thereon avacuumdeposited zinc coating, the metalized strips. are interleaved. Thesestrips are ordinarily slit from a wide web of the metal-coated paper,the strips being free of the metal coating in a band along one edgethereof. While the'metal-free bands can be produced as an incident tothe deposition of the metal coating on the paper, it is more practicalto apply the metal as an unbroken. film and to subsequently form themetal-free bands byremoval of appropriateportions of the metal coating.The metal-removing operationis customarily carried out before themetalized paper is slit to produce the condenser strips.

A principal object of thepresent inventionis to provide an improvedapparatus for removing predetermined stripes of such a metal i'coa'tingfrom a Web of the nonconducting:shet'material.

Another object of the invention is l to provide apparatus of the abovetypewhichisadaptedtto accomplish the clean removalof allimetal "inithearea to be striped, this.removal being accomplished at a high rate ofspeedsofsheetttravel without; danger of tearing of'the sheet material.

Still another object of the invention is to provide a process forforming metal-freestripes on metal-coated sheet material, 'whichisparticularly advantageous withresp'ect tocIeannessof the stripe andfreedom from any remaining metal particles in the striped area.

Other objects of the invention will in' part be obvious and will in partappear hereinafter.

The invention accordingly comprisestheapparatus possessing theconstruction, combination of elements and arrangement of parts,;and theprocess involving the several steps andthe relation and the order of oneor more of such steps with respect to each of the otherswhich areexemplified in'the following detailed disclosure, and the scope of theapplication of which will beindicated in the claims.

For a fuller understandingof-the nature: and objects of the invention,reference should behad to the following detailed description taken -inconnection with the accompanying --drawings wherein:

Fig. 1 is a perspective viewillustrating'in a diagrammatic fashion thepreferredembodiment of the present invention; and V I Fig. '2 is anenlarged, diagrammati sectional view of a portion of the apparatus ofFig. 1.

predetermined path during advancement. means for removing the band ofmetal coating In the present invention the apparatus comprisesa means,for advancing a web of a metalcoated, nonconducting sheet material, thismeans preferably advancing the web at a continuous high rateof speed.The apparatus also includes an electrical contact, positioned so astoengage the metal face of the web to maintain this metal preferablycomprises aplurality of electrodes which are successively positionableadjacent the metal coating as the metal-coated web is advanced. Each ofthese electrodes has a width,

extending across the advancing Web, which is on the'order of the widthdesired for the metal-free stripe. The apparatus includes a means formovingthe electrodes successively into and out of engagement with theweb, and a means for maintaining a sufficient potential differencebetween one of the electrodes, in contact with the Web, and the metalface of the web to create an arc between the metal coating and theelectrode,

this arcserving to vaporize the metal coat in the area to be striped.

-In a preferred form of the invention, the means for maintaining thepotential difference is so arranged that the potential difference,between the .metal coating and a particular electrode in con- :tact withthe web, is removed prior to the time that the electrode is moved out ofengagement with th webso as to prevent a drawing out of :thearc withconsequent irregularity of vaporization.

Thissheet is preferably advanced at a rate of approximately 200 feet perminute, and each electrode is in arcing contact with the metal coatingforabout one foot. each electrode be maintained at the potentialdifference required for arcing, up until the time that the nextsucceeding electrode has been brought .into engagement with the web andhas also been brought to thispotential difference.

It is also preferable that The electrodes are preferably mounted on acommon-support, suchas a wheel, the electrodes being in- .sulated fromeach other and being preferably uniformly arcuatelyspaced from eachother on the wheel.

Referring now to Figs. 1 and 2, the various features are shown inschematic form in one representative embodiment of the invention. Inthese figures the web of metal-coated sheet material is indicated at [0as being fed from one roll l2 thereof to a Wind-up roll 14 thereof,these two rolls being supported on suitable axles I E and 18respectively. For guiding the web in its path of travel, there areprovided guide rolls 20, 2| and 22, it being seen that guide rolls 20and 22 engage the metal-coated surface 24 of the web, while the roll 2|engages the upper surface 25 of the web. Positioned between the twoguide rolls 2i and 22 is the means for removing the metal coating 24from a predetermined area 25a of the web. This means comprises aplurality of electrodes 26. The outer end of each electrode 26 has awidth substantially equal to the desired width for th metal-free stripe,these electrodes being preferably mounted on a rotary support, such as awheel 28. Two electrode wheels 26, 28 are shown as being mounted on acommon shaft 29. The wheel 28 is preferably formed of an insulatingmaterial and carries the electrodes 26 uniformly arcuately spaced aroundthe circumference thereof. Near the center of wheel 28 the variouselectrodes 26 are exposed so as to provide a commutator which is engagedby a commutator brush 30 for successively energizing the variouselectrodes. In a preferred arrangement, the commutator brush 3D has anarcuate length slightly greater than the arcuate spacing of theelectrodes, so that two of the electrodes may be simultaneouslyenergized.

As seen best in Fig. 2, each of the electrodes 26 preferably includes aknife edge 32 for concentrating the are 34 created, as describedhereinafter, between the electrode 26 and the metal coating 24. Thisknife edge is slightly rounded, as at 33, to prevent tearing of the webH) as this web moves in a direction opposite to the movement of theelectrode.

As can be seen best from Fig. 1, the electrode wheel 26, 28 is sopositioned with respect to the straight line path between rolls 2i and22 that the electrodes 26 deviate the web H) only slightly from thisstraight line path. This feature of the invention is particularlyadvantageous in preventing tearing of the relatively fragile web l0.

For applying a potential difference between one of the electrodes 26 andthe metal coating 24, there is provided a source of electrical energy,preferably a low impedance source such as a battery 36, the positiveside of the battery being preferably grounded, and the negative side ofthe battery being preferably connected to the commutator brush 30. Forcompleting the electrical circuit to the metal surface 24, the rolls 20and 22 are also preferably grounded; This arrangement is particularlyconvenient since it allows most of the elements of the apparatus to beat ground potential while the electrodes and the commutator brush 30 areat a potential of about minus 20 volts.

The means for removing metal deposited on the electrode 26, as theresult of arc vaporization of the metal, preferably comprises a brush 38driven by a motor 40, the brush being preferably positioned near thebottom part of the path of travel of the electrodes. This brush 38 ispreferably mounted so that its axis is at 45 to the plane of rotation ofthe electrodes.

The means for advancing the web through the apparatus preferablycomprises a roll 42, driven by motor 44, roll 42 engaging the outersurface of the web roll M. The. axle l8, supporting roll I4, ispreferably provided with a floating mounting so as to permit axle i8 tomove away from the axis of roll 42 as the radius of web roll 14increases. The electrode wheel 28 is also preferably driven, through asuitable. connection, by means of motor 44.

In the operation of the device illustrated in Figs. 1 and 2, the roll 12of the web of metalcoated base material is suitably mounted in theapparatus and the web is fed past the rolls 20 and 2|, over theelectrode wheel 26, 28 and over roll 22. The end of the web is attachedto the floating axle I8. The device is then put into operation bystarting motor 44 to rotate the web roll 14. The web, as shown, travelsfrom right to left while the electrode wheel 26, 28 rotates in aclockwise direction. Thus the electrodes, while in engagement with theweb, are traveling in an opposite direction to the movement of the web.The wheel 28 is preferably rotated at such a speed that each electrodeis in contact with slightly more than one foot of web length perrotation of the wheel. As the wheel 28 rotates, the electrodes aresuccessively brought into contact with the web. As the first electrode(26a in Fig. 2) contacts the metal coating 24, which is at groundpotential, an are 34 is struck between the metal surface and theelectrode. This arc serves to vaporize the thin metal coating whichcondenses on the electrode 26a slightly below the tip 33 thereof. Thiscondensing metal, indicated at 24a, forms a shoe that extends from theface of the electrode and overlies the advancing metal coat. As themetal shoe 24a is built up, it acts as the source of the arc so that thearc moves farther and farther from the electrode. When about one foot ofcoated surface has passed electrode 26a, this electrode has meanwhilerotated so that the base thereof is no longer in contact with thecommutator brush 30. Shortly thereafter, electrode 26a moves out ofengagement with the web. Meanwhile the next succeeding electrode 26b hasbeen rotated into contact with the Web and its base has been contactedby the commutator brush 30 so that it is maintained at the minus 20volts potential. When this next electrode 26b first contacts the web,there is no arcing since it contacts only the metal-free paper base 25which is a nonconductor. When the preceding electrode 26a isde-energized, the arc is extinguished and the metal coat advances to thesucceeding electrode 26b. When the metal coat touches this succeedingelectrode 26b, the arc is struck and the metal stripe is removed fromthe advancing web as previously described.

In a preferred form of apparatus and process utilizing the invention,the metal-coated paper l0 comprises a thin condenser tissue 25 havingthereon a zinc coating 24 deposited from vapor phase in a vacuum. Such azinc coating has a thickness on the order of 1 micron or less, and isreadily vaporized by the arc 34 generated between the electrode 26 andthe metal coating 24. The electrodes 26 are preferably formed of brass,and the rolls 20, 22 are preferably also formed of a good conductor suchas brass or copper.

For simplicity of illustration, the electrical connections to only oneelectrode wheel 26, 28 have been shown. It is preferred to have each ofthe electrode wheels 26, 28, which are mounted on the common rotatingshaft 29, arranged so that corresponding electrodes are equallyarcuately spaced around shaft 29, each of the corresponding electrodesbeing electrically connected to a corresponding contact extendingbetween the various electrode wheels. This arrangement has the advantagethat a single commutator brush 30 may be employed to energize thecorresponding electrodes in the various electrode wheels.

Since certain changes may be made in the above apparatus and processwithout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description, or shown inthe accompanying drawings, shall be interpreted as illustrative and notin a limiting sense.

What is claimed is:

1. Apparatus for continuously forming a metalfree stripe on a web ofmetal-coated, nonconducting sheet material by removing a band of saidmetal coating, said apparatus comprising means for continuouslyadvancing the web, an electrical contact positioned to engage the metalface of the web, a plurality of electrodes successively positionable incontact with said metal coating, each said electrode being provided atits contacting end with a knife-blade edge having a width, extendingacross the advancing web, which is on the order of the width desired forthe metalfree stripe, means comprising a rotary member supporting saidelectrodes for moving said electrodes successively into and out ofengagement with said web, said rotary member being arranged to move saidelectrodes, while in contact with said web, longitudinally of said webin a direction opposite to the direction of advancement of said web,means for maintaining a sufficient potential diiierence between one ofsaid electrodes in contact with the web and the metal face of the web tocreate an arc between said metal coating and said electrode, saidlast-named means being arranged to remove said potential difierenceprior to movement of said electrode out of engagement with said web. andmeans for removing from each said electrode metal evaporated by the arewhich condenses on the electrode.

2. Ap aratus for forming a metal-free stripe on a web of metal-coated,nonconducting sheet material by removing a band of said metal coating,said apparatus comprising means for advancing the web, an electricalcontact positioned to engage the metal face of the web, a plurality oielectrodes successively positionable adjacent said metal coating, eachsaid electrode having a width, extending across the advancing web, whichis on the order of the thickness desired for the metal-free stripe, awheel, said electrodes being positioned around and extending from theperiphery oi said wheel, means for rotating said wheel so that saidelectrodes move, while in contact with said web. in a direction oppositeto the direction of advancement of said web, and a commutator forsuccessively energizing sa d electrodes as each said electrode movesthrough a predetermined arc of rotation. said commutator being arrangedto de-energize each said electrode prior to movement of said electrodeout of engagement with said web.

3. The apparatus of claim 2 wherein said arc o1 rotation is slightlygreater than the arcuate spacing of said electrodes on said wheel.

4. Apparatus for forming a metal-f ee stripe on a web of metal-coated.nonconducting sh et material by removing a band of said metal coating,said ap aratus comprisin means for advancing the web, an electricalcontact positioned to engage the metal face of the web. a pluralitv ofelectrodes successively posit onab e ad acent said metal coating, eachsaid electrode havin a width, extending across the advancing web. whichis on the order of the width desi ed or t e metal- Iree stripe, a wheel,said electrodes bein positioned around and extending from the peripheryof said wheel, means for rotating said wheel so that said electrodesmove, while in contact withv said web, in a direction opposite to thedirection of advancement of said web, a commutator for successivelyenergizing said electrodes as each said electrode moves through apredetermined arc of rotation, said commutator being arranged tode-energize each said electrode prior to movement of said electrode outof engagement with said web, and means for guiding said web along apredetermined straight line path, the axis of said wheel being spacedfrom said path by an amount only slightly less than the radius of thecircle described by the ends of said electrodes, whereby saidelectrodes, upon contacting said web, deviate said web only slightlyfrom said path.

5. The process of forming a metal-free stripe on a web of metal-coated,nonconducting sheet material which comprises advancing the web,providing a plurality of electrodes adjacent said advancing web, movingsaid electrodes successively into contact with the metal coating on theadvancing web, moving each electrode, whil in contact with the web, in adirection opposite to the direction of advancement of the web, applyinga potential difference between said metal coating and each electrodeduring a portion of the time each said electrode is in contact with theweb to create a metal-evaporating are between said electrode and saidcoating, removing said potential difference, thereafter moving saidelectrode out of contact with said web, and removing from said electrodemetal vaporized by said arc and deposited on said electrode.

6. The process of forming a metal-free stripe on a web of metal-coated,nonconducting sheet material which comprises advancing the web.providing a plurality of electrodes adjacent said advancing web, eachsaid electrode having a knife-blade edge, moving said electrodessuccessively into contact with the metal coating on the advancing web,moving each electrode, while in contact with the web, in a directionopposite to the direction of advancement of the web, applying apotential difference between said metal coating and each electrodeduring a portion of the time each said electrode is in contact with theweb to create a metal-evaporating are between said knife-blade edge andsaid metal coating, condensing evaporated metal on that side of saidknife-blade edge facing said advancing metal coating, maintaining saidare between said advancing metal coating and said condensed metal onsaid electrode, removing said potential difference, thereafter movingsaid electrode out of contact with said web, and removing from saidelectrode metal vaporized by said are and de-. posited on saidelectrode.

7. The process of claim 6 wherein each said electrode is maintained inarcing contact with about one foot of length of said metal coating.

GLENN L. MELLEN. VINCENT C. HALL, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Num er Name Date 1,909.0'79 Steerup May 16, 19332011.645 Miller Aug. 20, 1935 2,141,869 Konig Dec. 27, 1938 2,435,441Grouse Feb. 3, 1948

